Stabilized activators and their use in emulsion polymerization



droperoxide, or cumene hydroperoxide.

Patented Oct. 14, 1952 UNITED STATES PATENT orncs STABILIZED ACTIVATORS.AND THEIR USE IN EMULSION POLYMERIZATION Carl A. Uraneck, Burger,

Charles M. Tucker, Phillips, and Willard M. St. John, Jr., Berger, Tex.,assignors to Phillips Petroleum Company, a cor poration of Delaware NoDrawing. Application December so, 1948, Serial No. 68,422

23 Claims. (01. zoo -94.3)

This invention relates to polymerization of conjugated diolefins inaqueous emulsion. In one embodiment it relates to preparing syntheticrubber by emulsion polymerization using a highly active and stableactivator system.

In the production of rubber-like elastomers various polymerizationrecipes havev been developed in order to provide polymers of superiorphysical properties. Variations in operating [techniques .have also beenintroduced in order to effect further improvements in the properties i 1of the product. Recent developments have shown that synthetic elastomershaving greatly improved properties may be obtained if poly- Qmerizationreactions are effected at low temperatures. -Since conversionrates-generally decrease rapidly as the temperature is decreased, fasterrecipes are necessary in order that these reactions may be carried outon a practical basis. In order to accomplish the desired results atlower temperatures, a number of polymerization reoipeshave beenprovided. Outstanding among these are those in which a peroxide orhydroperoxide is a key component, and those in which a diazothioether isa key component. The peroxides and ,hydroperoxides are usually used inredox recipes, which include a combination of an oxidant, a reductant,and an oxidation catalyst. In this type of recipe the peroxide orhydroperoxide is the oxidant. The oxidation catalyst, is generallyselected from a group of materialsconsisting of compounds of metals suchas iron,

manganese, copper, vanadium, cobalt, etc. In

general it is assumed that the metal must be a ,multivalent metal and insuch a condition that it can change its *valence state reversibly. The

other ingredient ordinarily present is a reductantand is usually anorganic material such as a reducing sugar or other easily oxidizablepolyhydroxy compound. Compounds frequently'er'nployed in this capacityare glucose, levulose, soifbose, invert sugar, and the like. Astheoxidant in such a recipe, there may be used an inorganic peroxide, suchas hydrogen peroxide, a pernitrate, a persulfate, a, permanganate, orthe like, or an organic peroxide such as benzoyl peroxide, or an organichydroperoxide such astertiary butylhydroperoxide, methyl cyclohexylhy-In another type of recipe a diazothioether is the key component, andwhile it may be used alone, it is preferably used in combination with awaterfsoluble ferricyanide whichis a salt of a -monovalent cation, suchas ammonium or an alkali 1 metal In all of these recipes, it is usually{de 2 sirable to include a modifier, such as a mercaptan, and anemulsifying agent.

We have found that the oxidation catalyst used in such polymerizationrecipes is a very important part of the recipe, and that certainspecific improvements'in its preparation result'in "markedly increasingthe rate of polymerization and frequently also favorably influence thecharacteristics of the reaction mixture. Usually this oxidation catalystcomprises a compound of a multivalent metal such as iron, manganese,cop'- per, vanadium, cobalt, and the like, and most commonly is awater-soluble iron salt. The multivalent metal ion of such compounds canreadily pass from a low valence state to a higher valence state; andvice versa. Sometimes the compound, when present in its lower valencestate, can function in the dual role of reductant and oxidationcatalyst.

One commomy used redox catalyst is iron pyrophosphate. In a redox systemcomprising hydrogen peroxide and organic mercaptan, used as oxidant andreductant respectively, ferric pyrophosphate, prepared by addition 'of aferric salt to an aqueous solution of sodium pyrophosphate, has beenfound to be a useful catalyst. with another class of redox systems,comprising a cumene hydroperoxide (more formally designated dimethyl(phenyl) hydroperoxymethane) and sugar, ferrous pyrophosphate has beenfound to be more effective as a cata' lyst, as is more fully discussedin Kolthoff application Serial No. 751,955, filed June 2, 1947. However,ferric pyrophosphate can also be used. When carrying out apolymerization with the ferrous system, certain difliculties areencountered. For example, if the catalyst is prepared in the form of aso-called activator solution by adding ferrous sulfate to an aqueoussolution of sodium pyrophosphate, the solution must be used immediately,otherwise oxidation by the atmosphere destroys its potency. Impuritiesin the water, such as calcium salts, etc., likewise are deleterious. Iftheconcentration of ferrous ion added to the system is greater than theconcentration of the cumene hydroperoxide, i. e it there is present morethan one gram, or millition is retarded. Theexcess of cumenehydro-"peroxide required for optimum operating conditions over the mol ratioof one to one is critical so that slight errors in measurement oftheseingredients can" easily cause great difierencesin the rate ofpolymerization and in the extent to pIieite "activators; aith-the" likwhich polymerization .proceeds. However, it

In preparing activator solutions, errous' or ferric salt is added to asolution of sodium pyrophosphate. Ferrous and ferric pyrophosphate areformed by metathesis and these compounds combine further toformipyrophosphatel-icomy plexes, such as, the wellknownfi'stilub'leferric this reason it has become c steamy ferrouspyrophosphate anderric ,py ro ferrous or ferric ions, that is,whetherderived mentioned that the aforementioned soluble ferv fr icpyrophosphate has'Jaeen found to be a-very cb nvn i eht satire eldf 1' fei'fic fi o'ns if of the" 41172616232- t ion of ferriclactivatdr i f 'es6i .cumene hydroperoiiidewith"i'sp 'to fe'r eusiiehmiist ihe p esehtto:obtain i-dpt' um lijolymeriz'atioh."""WithTerr fth'efljotherihahdj thisIiii it I peiymerizaftien "ea'hihe 'hducte'dw'i'th" mounts ,eteiimeheiyaiehemxid :areim thelh are required withan "eilliivalentlcd h tion erl'ferroiis salt." however, under. the best attainable cO IidifiiOIis''ith fate of "poiyeiization cent of i's'ordinarilylho rasterthah about67-15 fw et eah h 'fehtainea with "ferrous"- gzphate. itifiightibthought" mixture er ieireusaharerrie salts would pesses'seertaihaavantag s "and suehi H the 'e'esei With suchmhafires'rthe'iiznitih ratio ot cumene. thydroperoxideftoiron canbelowered ySt -s ch as j discuss'ed,-siirprising i provements 7 tain "inthe.Ipolyiiferizationirate} and also ;o'f.te fluidity .off'thtiesuitiiheiate when eertain inorganic "waterisoluble salts whiohhavefe'di'i ng properties are-incorporated in the aetivater so iitiehwhiehieehtai s" the oxidation c'atal'y'st. 1K0; cording to'hur inv'entionftheativatorsoliitidn is p eper'ed' by i seivin'g-"ihwe'ter ajsa'It er anihiv,tlvalent mtal-s'uhas"previously discussed, :a

,pyrbphosphate' 'of a,monovalenticatioh, such as alkalimetal'orammonium, ancla'saltlof a mono- 'rit cation and anlinorgani ariio'nwhic'h is' a l reducing'fagent, such as 'a"'hyDObhosphite,"fthioe:ducing salt is also preferably a {salt ofian alkali ,metal or ammonium,and its'lpre'senceiso stabilizes .f the activator composition "thataniner't' atmosreactions. These activators are'unus'u'allyversa-- inthat"they'are applicabl'e'in' recipes'contain l ing 'very smalramo'untsof'iron; or other *muiti- "rdphos-,- I V 35, ing, but behen-eiarstabmetizatientei ta con ugated "dieie h' car- I f gas'bia ketirrgmayb ut'tolpfoducesynthti'cfr'uhberina's stem";

70 use, activator valent metal, say :.01 millimol ofsalt per 106 gramsof monomers, or they may be employed when themultivalent metal contentis as high ,as 3. 0 millimols per 100 grams of monomers.

fiihe'se inorganic reducing salts, used in accord- 10 'ioni-wh'enitislipresent ineither a low or a high pyrophosphate, F84 (P207) 3=3Na4P2O7-xHzO. For to speairci ideihe activators without specifying thesource of the I Jwheh itiisiipr'ese'rit in a high valence state, the

fsa'lt: should'befihesen so that resulting reaction .15 products are notharmful to the polymerization from ferrous sulfate. or some othersaltifa-nd Without s eci yi g to what extent the resulting; Ipyrophosphates have been complexed; IQHcan- -be reactionJand -a"sumcientamount of salt should 'be' used so that a substantial proportion doesnot enter into such a reaction. We prefer to prepare the activatorsolution with the multivalent metal in its lower valence state, and insuch instances fthe'iise'of'h'separatereiiuctant ih'the' polymeriza-"tionfsys'ten i i ""irequently unnece s ry, particularlywhenioperatin'g' at subffreezing' poiym'ema- "'tio'ntemperaturewith anial'coholpresent"in?the aqueous medium; *wheriithe activ'ator solutiori'is jipreparedwith arsart ioi a'mi'iltivaleiit, metal itshigher""va1enceistat e it is"hsiialiy necessary also tohave are'd'trctant su dhas ta reducing; sugar,

"present "while the isolation is heated: If desiredultivalerifmetaliis'preseiitin its'fiower valence estate; H,

The additional ingredientfisprererably interporate'dinto'theac or"solutionfpridrfto at- "added 'to"'the "solution" aftefheatingfif-this"l'1e'ating is carried dutfin theiahsence of cbhta'et with freeoxygen. the components are "mixed :prio r -toj heating and "thef'resultih'g ,somtioh' is "heated'fin thepr'esehce cf-air; theres'ulting"compos'ition'tah bestored ior'a' period 'o'ffrom se'v-*eralfhours'toseveralj'days, say"? to 15"d'ays, with substantially no"loss" ofjac't'ivity. If "desired inert "tibhisthafthe'actiVator' cahbel' iepa-red in 'the presence"oi ire'efcgygeh; In order to i-get out.imfpfoved'fresults "tofthefgreatest extentit "is necessa'rytoad'd"theirr ultivalentmetalsalt; pyropnospirate; 'and'jthird'salt to.water and then toheat "the resultingsolution itoj a temperathrepetween 140 an'djIOO C.

An object of' thi ve'nti'on' 'toipojlymerize 'unsaturated 'organic,bolfip ound's. 1 A other object' ofthi's inventi n isto produce" ahimroved synthe'tic"rubber. Stiihano'ther bject ofthis'ihvention is' toincrease the reaction rate fi'h f pe1ym'erizing j *unsaturated "organiccompound :jih

.aqueous"emulsion. additionalobjec't ofthis "invention is to produce "amore fluid synthetic rubber latex when eifecting'emulsion polymerizationat subfreezin?temperatures. [Still another tive activator solutio'nffousei'inemulsio'n polymerization, wherean' oxidant is 'an"e'ssentia1 irirgredient-oi thepolymerization"mixture; A further object of "thisinvention is to "provide; anti I compositions: 'comprisihg'apyro-"phosphate of a multival'e'nt 'metalfwhich is stable in" the presence offires oxygen. Ai still further object of our vention istofpr'ovidafanduse,"a

"objector this invention is toprjoduce a fmoreacstable ferrouspyrophosph'ate"activator solution for use inemulsion-polymerization;"Furthefobilizingeife'ctsresultifiitis :Iects and advantages of thisinvention will become apparentQto one skilled in theartffrom the"accompanying disclosure and discussion.

i In effecting emulsion polymerization of a mono.-

meric material, particularly when a batch-type orsemibatch-typeoperation is carried outgthe reactor is usually firstcharg'ed with theaqueous medium, which contains the desired emulsifying agent, and themonomeric materialis then admixed .with agitation of the contents. .Atthe same time a reaction modifier, such as a mercaptan, is alsoincluded, usually in solutionin at least a part of the monomericmaterial. An activator solution and an oxidant are separately added tothe reaction mixture, and reaction then proceeds. .A preferred manner.of addingathese twopconstituents is usually to have the activatorsolution. incorporated in the aqueous medium prior to addition of themonomeric material, and .to add the oxidant as the last ingredient.sometimes; however, satisfactory polymerization resultsican be obtainedwhen this procedure is reversed... It is also sometimes the practice toadd portionsuof one or the other of the activator solution and oxidantintermittently, or continuously, -during,the course of the reaction. Ifthe 7 operation is carried out continuously,

streams of the various ingredients are admixed in somewhat the sameorder prior to their final introduction I into ,thepolymerizationreaction zone.

The activatorsolution which is prepared in accordance with our inventionis usually prepared entirely separately and somewhat prior to its use inthe polymerization reaction- Each in.-

gredient is dissolved in water in a concentration between about 0.1 and10 parts by weight per lOOparts of .yvater used for the activatorsolution. The three essential ingredients hereinbefore discussed areadded to water and theresulting solution heated to a temperature between40 and. 100 C., preferably between 50 and 80 C., for a period of from 5to 90 minutes, more usually from 30 to 60 minutes. In the majority ofcases, the salt of the multivalent metal and the pyrophosphate arepresent in anamount ranging from 0.8:to 1.2 mols with respect to one molof the ,other,.and the resulting activator solution, ,and oxidant aresubsequently addedto the polymerizationzone in amounts so that therelative amounts of thesematerials are within the samefrange. It.isusually preferred that the .gamounts of multivalent metal ion andpyrophosphate be present in equimolar quantities, and" the amount ofoxidant be in excess of the molecular equivalent of the multivalentmetal and pyrophosphate. We prefer to see to it that the strength of ouractivator solution is so regulated, and the amount of the activatorsolution added lisy'also so regulated, that there is, added to:thetreaction mixture from 0.01 to 3 millimol parts :of multivalent metaland .pyrophosphate and oxidant per 100 parts by weight of monomerismaterial,*with the preferred quantities being in the range from 0.1 to0.65 millimol parts by weightjofwmultivalent metal. The amount ofreducingsalt present in the activator compositiom that is,thdhyriophosphite, thiosulfate; or other compound hereinbeforementioned, is often expressed in relationship to the monomersemjplo'yed. The quantity of this ingredient win generally not exceed onepart per 100 parts of finonomers and in most instances the amountrequiredto produce stabilization of theactivator is lessthan 0.5 part,say from 0.02 to' 0'.30 part. meandering the amounts of these materials,

the same units of weight shouldbe used. That is, if the monomericmaterial is measuredin pounds, these other materials are measured inmillipound mols.

As previously stated, it is usually desirable that the multivalent metalbe present in its .lower valence state. With some recipes, it isunnecessaryto include an organic reducing agent either inthe activatorsolution or in the polymerization mixture. However, particularly attemperatures above 0 C., a faster reaction is sometimes obtained withsome recipes when a small amount of an organic reducing agent, such as.a reduc ing sugar, is included in the polymerization recipe, and it isfrequently more desirable to incorporate this in the reaction system byfirst including it in the activator solution along with the otheringredients. When the multivalent ion is present in its higher valencestate, it is usually necessary to include in the activator solution anorganic reducing agent. As a result the multivalent ion will bepartially reduced and .a. substantial amount of the multivalent ion willbe present in its lower valence state when the activator solution isready for addition to the polymerization mixture.

It is usually preferred that the multivalent ion be iron, and theactivator solution maybe prepared from any of the readily availablesoluble iron salts, such as ferrous sulfate, ferric sulfate, ferrousnitrate, and the like. A pyrophosphate of sodium or potassium is alsousually used in preparing the activator solution. Apparently the ferroussalt and the pyrophosphate inter-react to form some kind of a complexcompound. The third salt added in accordance with the present inventionnot only tends to stabilize the aqueous solution of such a complex fromdeleterious effects of free oxygen, but may also influence in some waythe composition or molecular structure of the resulting complex.Previous experience with the preferred types of recipes has indicatedthat it is necessary to incorporate at least 0.3 part by weight of ironsalt mixture per parts of monomers in order to obtain satisfactoryreaction rates and conversions. This corresponds to at least about. 1.1millimol parts of iron per 100 parts of monomers charged to the reactionsystem. We have discovered that when the activator solution is preparedas disclosed herein, satisfactory results can be obtained with an amountof iron no greater than 0.5 millimol parts per 100 parts of monomerscharged. As a result, the final polymer product contains a substantiallylower quantity of iron, which is distinctly desirable insofar as theproperties of the resulting rubber product are concerned.

The monomeric material polymerized to produce polymers by the process ofthis invention comprises unsaturated organic compounds which generallycontain the characteristic structure CH2=C and, in most cases, have atleast one of the. disconnected valences attached to an electronegativegroup, that is, a group which increases the polar character of themolecule such as a. chlorine group or an organic group containing adouble or triple bond such as vinyl, phenyl, cyano, carboxy or the like.Included in this class of monomers are the conjugated butadienes or1,3-butadienes such as butadiene (LIi-butadiene) 2,3 dimethyl 1,3butadiene, isoprene, piperylene, 3-furyl-1,3 -butadiene, 3-methoxy -1,3- butadiene and the like; haloprenes, 811611 was chlor'op'rene:(Z-chloro-1,3:butadieneh b. ;om,q,-

'ketone, .methyl yinylethinyl alkyl. carbinols, vinylzacetate; vinyl.ipjre'neh methylchloroprene :(Z-chlpro-t-methyl; .133 i-doutadiene)and. :the. :like; waryl; olefins such: as.":..styrene; various.:alkyl... styrenes, p chlorostyrene, p methoxystyrenaxalpha'methylstyrene,;.vinylnaphthalene andxsimilar :deriyatesthereofiaand thelike;v acrylicIand1substituted acrylic acids. and; their esters,-nitriles and....ami.des such. asacrylic acid,;:methacrylic-acid',.:;methyl acrylate, ethyl. acrylate, methyl alpha-phloroacrylate, methyl methacrylate, ethyl; methacrylate; .butylimethacrylate,.methyl ethacrylate, i, crylonitrile, .methacrylonitrile, methacrylamide:andthe like,.methyl..isopropenyl vinyl .ketone, methyl vinyl: ether,

chloride, vinylidene chloride, .vinylfurane, Vinylthe "liquid.monomeric, material; to; permit. satise factory operation..If.'theresultinslatex tends to gelat low reaction. temperatures; a;larger; pro.- portion. of aqueous; phaseshould bei used. I i generallypreferred that the. emulsionzberof. an Oil inwater type, .withthe ratioof aqueousme i m to monomeric. material between'about .1i.5.:l andabout:2;75.:1,;in..parts by. weight. In.theprac.- tice of theinventiongsuitable.meanswillbe necese sary; to establish; and maintain;anz;emulsion.:and to remove reaction..,heat: to. maintain. a. desiredreaction temperature. The: polymerization: may

carbazole, vinylacetyleneand other unsaturated v hydrocarbons,..esters,; alcohols, acids, ethers, et.c.., of the typesdescribed. Such.unsaturate.d:com.- =poundsamay- .be. polymerized ralone, :inwhich-..case simple :linear polymers are formed, or; mixtures offtwo or'more: of: such. compounds which; are :copolymerizable" with each otherin aqueous emulsion may be "polymerized. to .form linear 'copolymers.

The process of this invention is. particularly be conducted. in batches;.Jsemicontinuously, .or continuously. The. :totalpressure. 'on. the 1reactants is preferably "at least raspgreatas the: total vaporpressureofi the mixture, :so that the initial reactantstwillbepresentinxliquid:phase... Usually .50 :to 85 per: cent .of themonomericmaterialis polymerized.

Emulsifyin'g: agents which are. applicable: in these low temperaturepolymerizations: are materials such. :as apotassiumxlauratep potassiumoleate, and :the like. However, other emulsifying agents, such asnon-ionic emulsifyingagents, salts .of alkylaromatic sulfonic .acids,salts of alkyl sulfatesyandthe like which will produce efiective whenthe. monomeric material polymerized is a polymerizable aliphatic;conjugated diolefin: .o'n'ua' mixture. of: such a. conjugated 'diolefinwith. lesser amountsxof one .orv ImDIZBLOthGI v compounds containingan-active .CI-I2=C group which are :copolymerizable therewith such:asxaryl olefins, acrylic and substituted acrylic: acids, esters,nitriles and amides, methyl. isopropenyl ketone; vinyl." chloride, and.similar compounds mentioned hereinabove. Inthis "case the prod,-

.-u'c ts -of the polymerization. are high molecular pounds of boththe-monohydrie; andiipolyhydric I types, and include methyl alcohol,ethylene glycol, glycerineperythritol, andthe like. "The amount ofalcoholic ingredient used. inxa polymerization recipe must be.suilicient" to. prevent freezingof theaqueous phase and generallyirangesflirom 20 to 8'0 parts per 100 parts of inonomers charged; Inmost cases-.-.the ..amount 1'01 water employed is sufiicient. to :'make:the total quantity of the alcohol-watermixture;-equal 180' parts' Incaseswhere it is desired t'o' usea larger quantity ofthealcohol-watermixture, say around 250 parts, thefam'ount; ort'ialcoholatmay beincreased to as much: as120parts; It: is: -pr.e-'

ierred that the alcohol be such that iUlSTSllbStfiiIltially-insoluble inthe non-aqueousvphase; and that 90' per cent, or more, ofthe alcohol:present he inth'e aqueous phase. A.'high'eboilingfalcohol 'suchasglycerine' isdifiicult' to recoverifrom-the resulting serum;alow-boiling alcohol such as methanol is easily removed-andfrequentlypreierred. Other low-boiling; .1 alcohols 1 such 5 j; as

"ethanol, however, are. frequently tooisolubleirin this'inventionmay'range from favorable results under the conditions ofthe reaction,can also be used'in practicingfi'theinvention. I

The pH of the. aqueousphase may bevaried over. a rather wide rangewithout: producing deleterious efiects on the conversion rate-or theproperties of the polymer. general the pH mayv be within the range of910 to 11.8, with the narrower range of 9.5*to 10.5 being mostgenerallypreferred; 7 a

The mercaptans applicable-ln-this invention arerusuallyr alkyl'mercaptans, and these maybe of primary, secondary, or tertiaryconfiguration, and generallyrange-from Ca to-Cm-compounds, but may havemore oriewer carbon atomsmer molecule. Mixtures or blends of mercaptansare also; frequently considered desirable and in many cases arelpreferred to the pure compounds. The amountxof 'mercaptan employed will.var-y,:dee pending upon the particular compound or blend chosen, theoperating temperature, the freezing point: depressant V employed, -andthe results desired. In general, :greater modification is:ob.-

tained when operating at low temperatures and therefore a smaller amountof mercaptan lszadd ed to yield a product-of'a given Mooney value,

than is used at higher temperatures. In'theicase' of'tertiarymercaptans;such as tertiary camercaptans, blends of tertiary C1 2, C14,.and Ciemercaptans, and the like; satisfactory modification is obtained with 0.05to' 0.3: part 'mercaptan .per lofl parts monomers, but. smaller orlarger amounts may be employed insome instances; In fact. amounts aslarge as 250 parts per- 100: iparts of monomers may'be used. Thustheamountoi -mercaptan-isadjusted to suit the caseathand'.

Temperatures applicable for'the' operation of +401to +-9 C;, with therange -2o-m +5*C.' being: preferred.

Our new: activator solutions :can bexused'itoiacl'e vantage in :systemswherein the;;'oxidizing; agent is a. peroxidic-type material, orv a-compoun d which functions in thecapacity of ans-oxidizing 'agent, such-'as adiazothioether which is soluble in a, liquid. hydrocarbon material,suchasliquid .butadiene.

We prefer to use organic peroxides and .hydroperoxides', such as may-be.represented by; the formula'ROQR'f, whereR" may be an lene. and thelike. 1 H 1 Advantages of tie" invention are illustrated by thefollowing examples- Q air" by dissolved in 12 parts water. turewash'e'ated to 60 C. and allowed to cool heferred rdiazothioethersinclude 2'-.(4 -methoxynaphthalene, 1- -naphthabenzenediazothiomercapto) (zA-dimethylbenzene diazomercapto) The reactants, andtheir proportions, and the other specific ingredi ents of the recipesarepresented asbeihg typical and shoul'd not b construed to limit theinvention'unduly. r

1 I e M Example I e W "The" following recipe was, employed for .carryingputgabutadiene styrene copolymerization rei Parts by weight Butadiene1'71,

Styrene 29 Water- 180' Methanol 40 Potassium laurate..- a 5.0 Mercaptanlolend l Variable. (jui'jnenahydroperoxide; 0,264 11.75

' l millimols) Condensed alkyl acid sodium salt r 0.02 Activatorsolution:

Ferrous sulfate, FeSO4.'7 HzO 9.31 (1.11

millimols) M a millimols) un ypophosphit V e A blend of tertiary c agatec1, al1pliaticmercaptans in a. ratio of 3 1 z 1 parts by weight.

The activator was prepared in the presence of dissolviiig l'ithe ferroussulfate 12 parts water and adding it to a mixture of the sodiumpyrophosphate and sodium hypophosphite previously- The resulting mixforebeing used. When carrying out a polymerizattion, all materials werecharged to the reactorin the conventional manner, the cumenehydroperoxide being added after the temperature was .ad-. justedto 10 C.I i. i

Several parallel-runs were made as follows: (a) Run I, activatdr'usedimmediately after preparmors-m rurillfactivator aged in air 18 hoursbefore use; run III, activator used immediately after preparation; (11)run. IV, activator made under nitrogen atmospherand used immediatelyafter preparation; (e) runrVi, activator made under nitrogenatmosphere'and'aged in air 14.5 hours before use; (I) run VI, controlactivator prepared under nitrogen atmosphere without sodiumhypophosphite (0.42 part sodium pyrophosphate used). The results wereas" follows:

Time to Beach 60% Conversion,

Hours Mercaptan Blend,

Run No.

. Parts p pphespiiategmm oa 033611.26

7 Potassium laurateIpl-I i Two further parallel runs were made, usingslightly difierent recipes, in which the activator did not contain astabilizer. In one case nitrogen blanketing was used during thepreparation of the activator while in the other case no method ofprotection was employed except that the activator Mercaptan blend rCumene hydroperoxide Activator solution: i-

Ferrous sulfate, FeSOr'ZI-IzO Sodium pyrophosphate, Na4P20'z 0.42Potassium chloride 0.4

1 A mixture of tertiary C C14, and C 9 aliphatic -mer-- captans in aratio of 3 1 1 parts by weight.

added, with the activator solution, to a' reactor after which thestyrene and mercaptan were charged. The butadiene was then added, thetemperature adjusted to 10 0., and thecurnene hydroperoxide introduced.No polymerization had occured at the end of 12 hours.

- The second parallel run was made using the same recipe andtechniquabut in thiscase the activator solution wasblanketed withnitrogen during its preparation and the mixture was agitated onlymildly. Polymerization was-effected at -10 C. according to theconventional technique. A conversion of 59 per cent wasoba nedin l v r-l ,vThese results, considered together with therpre viously presentedruns; show ,the ,deleterious r fects of air (free 7 oxygen) upon;theactivator spliii tign when no; reduc ng salt ,is, used, and -alsqqthefactthat the use of a reducing salt in theactiv m tor solution obviatesthis deleterious action pfr free oxygen.

. ii n zal t was carried out at 10 Crasinfthe prece r uns. A 60 per centconversion was obtain l3z2hours.

Example Hf a i Butadiene was I co polymerized f tyrene at 10? C,.;,aceording. to the following reflcip Partsby'w'eight Butadiene ,79-Styrene Water Methanol Conversion,

Time, Hours Percent Example IX Three activators were prepared in thefollowing manner: i e

I. A mixture of 3.1 grams FeSO4.'7I-I2O, 5.0 grams Na4PzOm10HzO, 1 gramNaHSOa, and sufficient water to make 100 m1. of solution was. preparedunder nitrogen and heated at 60 C. for 40 minutes. i

II. Sodium hyposulflte was substitutedfor sodium bisulfitein I.

III. A control activator was prepared by heating a mixture of 3.1 gramsFeSOa'lHzO, "7.0 grams NflZP lOfi-IOHfiO, and sufficient water to make100 ml. of Solution at 60 C. for 40 minutes under" an atmosphere ofnitrogen.

After being stored in air tions in activators I and II were water whiteand no crust had formed on the precipitate. In the control activator thesolution was brig-ht yellow and a crust had formed on the precipitate.After being stored the control activator had oxidized to such an extentthat it would not give satisfactory results when employed in apolymerization reaction. No noticeable reduction in activity wasobserved with the first two activators.

Example X a at -l0 (7., using the following recipe:

. Parts by weight Butadiene 70 Styrene 30 Water 192 Methanol 48Potassium laurate (95% neutralized) 5.0 Mercaptanblend 1 0.25 Cumenehydroperoxide 0.084 (0.55 millimol) Activator solution:

Ferrous sulfate,

FBSO4.'7H2O Sodium pyrophosphate,

NmPzO-zlOI-IzO Sodium hyprophosphite,

NaI-I2PO2.H2O

(Variable) A mixture of C11, C14, and C15 tertiary aliphatic mercaptansin the ratio of 3:1 :1 parts by Weight.

' quantities. The activator solutions were so prepared, and subsequentlyadded in such amounts, that the ingredients were added to the reactionmixture in the amounts indicated in the followingtable Thepolymerization results (conversion) are also recorded in the table.

24 hours, the solu- 4 Percent Conversion at (12 hours Ferrous Sulfate la sodium Pymphosphate 0.5 millimol 1.0 n11l11mol 2.5 milhmol SodiumHypophosphite (Parts by Weight):

These results show that at the 0.5 millimol initiator level sodiumhypophosphite accelerates the reaction, at the 1.0 millimol level it hasmuch. less effect, and at the 2.5 millimol level itbehaves as aretarder. A method has therefore been provided for increasing the rateof reaction of low iron content recipes. Reference to these data alsoreveals that the iron content of the recipe must be doubled in order toobtain the same rate that can be obtained by the addition of sodiumhypophosphite to the 0.5 millimol level recipe.

As will be evident to those skilled in the art, various modifications ofthis invention can be made, or followed, in the light of the foregoingdisclosure and discussion, without departing from the spirit or scope ofthe disclosure or from the scope of the claims. 1

We claim: s

1. A process for polymerizing an organic monomeric material comprisingan unsaturated-organic compound containing a CH2:C group while dispersedin an aqueous medium, which comprises polymerizing such a monomericmaterial while dispersed in an aqueous medium inthe presence of anoxidant and in the presence of an activator composition prepared bydissolving in water a salt of a multivalent metal capable oi existing intwo valence states under such conditions that it is present at least inpart'in a lower valence state together with a pyrophosphate of amonovalent cation selected from the class con sisting of alkali metalsand, ammonium and with a reducing salt ofa monovalent cation selectedfrom the class consisting of alkali metals and ammonium and of aninorganic anion selected from the class consisting of hypophosphite;

thiosulfate, sulfite, bisulfite and hyposulfite, heating said solutionto 40 to 100 C. for 5 to minutes and subsequently cooling said solution,and adding the cool solution to saidaqueous dispersion, the amount ofsaid solution added and the amount of said constituents present in saiddispersion being such that, per parts by weight of said monomericmaterial, there is added 0.01 to l millimol part of each of saidmultivalent metal and pyrophosphate and 0.02 to 1 part of said reducingsalt, and said oxidant is present in an amount in excess of onemolecular equiv alent of said multivalent metal.

2. The process of claim 1 wherein said polymerization is conducted below0 C. in the presence of an organic hyproperoxide as said oridant. 3. Theprocess of claim 1 in which said'difie'rent salt is a hypophosphite ofanalkali metal. 4. The process of claim 1 in which said different salt isa thiosulfate of an alkali metal.

5. The process of claim 1 inwhich'said different salt is a bisulfite ofan alkali metal.

6. A process forpolymerizing-an organicmonomeric material comprising anunsaturated organ ic compound containing a CHz:C -group while dispersedin an aqueous medium, which comprisespolymerizing :such a imonomericmaterial while dispersedin anaqueous mediumin the presence compositionprepared by dissolving in water a salt. ofa multivalentmetal "capable'of'existin'g' in two valence states under such conditions that it-Jispresent at least in part in a lw'er valence state together with'apyrophosphateof a, monotalent cation selected from the classconsisting of alkali metals and ammonium and with a reducingsalt of amonovalent cation selected from the classconsisting of 1 monium.and-ofan inorganic anion and which has no adverse. effect valentmetal,Lheatinglsaid solution to 40 to 100? C. .for,5 to :90 minutes andsubsequently cooling Said.. solu'tion,. and adding the cool solution :tosaid aqueous dispersion, the amount of saidsolution added.,and .the.amount of said constituents present. in. said dispersion being suchthat, .per 100, parts by Weight of said monomeric material,

there is added 0.01 to 1 millimol part of eachof said multivalent. metal.and pyrophosphate and 0102 to l part of said reducing salt, and saido'xidantis present in an amount in excess ofon'e molecular equivalent ofsaid multivalent metalq improved process for producingsynthethic rubber,Which comprises polymerizing a monomeric material comprising1,3-butadiene while dispersed in'an aqueous emulsion in the presence of'dimethyl '(phenyl) hydroperoxymethane as an oxidant and in the presenceof an activator composition prepared and a hypophosphite of a monovalentcation selected from the class consisting of alkalimetals';

and ammonium, heating said solution to a temperature between 40 andf30C. for 'a period of 5' to 90 minutes and cooling said solution, andadding the cool'solution tothe reaction mixture,

the 'amount'of said activator composition added position,the'improvement which comprises usoi an oxidant and in the presence ofan activator alkali metals and -am-' upon-ions of said multi- I bydissolvin in 'water ferrous sulfate, sodium pyrophosphate Iandjoxidantand .oflatoionepart-oi said different ing as an activatorcomposition comprising said iron pyrophosphate an aqueous solution pre-'pared by dissolving in water a soluble iron salt under conditions suchthat at least part of said iron is present. in. the ferrous state, apyrophosphate of a monovalentxcation selected from the class consistingof alkali metals and ammonium, and a difierent salt of a monovalentcation selected from, the class: iconsisting of alkali metals andammonium and an inorganic anion which is a reducing agent and has noadverse effect upon iron ions, heating said solu-* tion to a temperaturebetween 40 and-100- C. for 5 to 90 minutes and subsequently cooling theresulting "solution, and so incorporating said solution in said aqueousemulsion along with said oxidant that there is added, based upon 100parts by weight of said monomeric "material, 0.01 to- 3 millimolparts ofiron, pyrophosphate,

salt;

,9. In the analyst polymerization of a mo; meric material comprising aconjugated diolefin while dispersed in an aqueous emulsion toproduce'synthetic rubber, in which a polymerization catalyst is usedcomprising an oxidant and a pyrophosphate of .a multivalent metalcapable of existing in two valence states as an activator composition,the improvementllwhich comprises using as said activator composition anaqueous solution preparedby dissolving in water a pyrophosphate of ,amonovalent cation selected from the class consistingfofalkali' metalsand ammonium, a salt of such a multivalent metal under cOnditionssuch'ithatiiit is: present: atsleast .in

1 part in a lower valence state, heating .said-solua tiontoiatemperature between 40 and.100 C. for

5 to .QOminute'sLnnder conditions. such :thatziree oxygenqzdoesc notIhave a harmful effect upon said multivalent: metal and subsequently.cooling the resulting solution, incorporating. insaid solu-- tion duringsaid. preparation a' difierentsalt of a monovalent cation selectedfromthe class con sis'ting of alkali metals and: ammonium and :aninorganic anion-'Iwhichis a reducing. agent and has no adv'erse effectupon ions of. said multivalent metal, :and so incorporating saidsolution in said polymerizationw'along with-said oxidant that there is.added,pbased 'upon parts by weight or said-:monomeric materiaL. 0.01 to3 millimol parts, 'of saidfmultivalent metal, .pyro-' phosphate and.oxidantr'and. 0.02 to one part of said; .diflferent 'salt. 1

l0'.:; .The'-pr0ces's1 oiuclaim. wherein said oxidant-:is an organichydroperoxide, .said multi-: valentmetal is ironiand-isaddedtosaidactivator solutions as .a ferrous. saltv in the. absence of anyreductant; and said activator composition. andoxidant areseparatelyadded to said polymerization in such amounts that there are equimolaramounts of iron and pyrophosphate and a molar excess of said oxidantover said iron.

phite, thiosulfate, sulfite, 'bisulfite and hypo- 12. The process ofclaim 9 in which said different salt is added to said solution prior tosaid heating.

13. The process of claim 9 in which said solution is heated in theabsence of contact with free oxygen and said difierent salt'is added tosaid solution subsequent to said heating.

14. An improved method of preparing a solution of iron pyrophosphate,which can be used as an activator solution in the polymerization of aconjugated diolefin while dispersed "in an aqueous solution in thepresence of arr-oxidant, which comprises dissolving in" water a solubleferroussalt anda soluble pyrophosphate in equimolar amounts and a saltof a monovalent. 03,-! tion selected from the class consisting of alkalimetals and ammonium and an inorganic anion which is a reducing agent andhas no adverse eife'ct upon iron ions, each in an amount between 0.1 and10 p'ar'tsby weight per 100 parts of water, and heating 'the'resultingsolution to a temperature between 40 and 100 C. for-5 "to can be used'as an activator solution in the poly valent metal is iron,

, selected from 17 merization of a conjugated diolefin while dispersedin an aqueous emulsion in the presence of an oxidant, which comprisesdissolving in fwater a salt of a multivalent metal, capable of existingin two valence states and under such conditions that it is present atleast in part in a lower valence state, a soluble pyrophosphate in anamount at least stoichiometrically equisolution to a temperature between40 and 100 C. for to 90 minutes.

16. The method of claim wherein said multiand said heating is at atemperature between 50 and 80 C. for to 60 minutes.

17. The method of claim 15 wherein said multivalent metal is iron andsaid anion is selected from the class consisting of hypophosphite,thiosulfate, sulflte, bisulfite and hpyosulflte.

18. As a composition of vmatter, an aqueous solution prepared bydissolving in water a ferrous salt, at least an equimolar amount of apyrophosphate, and a salt of a monovalent cation the class consisting ofalkali metals and ammonium and an inorganic anion which is a reducingagent, with an amount of each between 0.1 and 10 parts by weight per 100parts of water, and heating said solution to a temperature between 40and 100 C. for 5 to 90 minutes.

19. The composition or claim 18 wherein said salt is a sulfite.

20.,The composition of claim 18 wherein said salt is a hyposulfite.

21. The composition of claim 18 wherein said salt is a thiosulfate.

22. The composition of claim 18 wherein said salt is a bisulfite.

23. As a composition of matter, an aqueous solution prepared bydissolving in water a ferrous salt, at least an equimolar amount of apyrophosphate, and a hypophosphite of a monovalent cation selected fromthe class consisting of alkali metals and ammonium, with an amount ofeach between 0.1 and 10 parts by weight per 100 parts of water, andheating said solution to a temperature between 40 and 100 C. for 5 tominutes.

CARL A. URANECK. CHARLES M. TUCKER. WILLARD M. ST. JOHN, J 11.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,366,328 Fryling Jan. 2, 19452,367,877 Layng Jan. 23, 1945 2,380,473 Stewart July 31, 1945 2,380,614Semon July 31, 1945 2,471,938 Crouch et al May 31, 1949 OTHER REFERENCESInd. & Eng. Chem., May

1. A PROCESS FOR POLYMERIZING AN ORGANIC MONOMERIC MATERIAL COMPRISING AN UNSATURATED ORGANIC COMPOUND CONTAINING A CH2=C< GROUP WHILE DISPERSED IN AN AQUEOUS MEDIUM, WHICH COMPRISES POLYMERIZING SUCH A MONOMERIC MATERIAL WHILE DISPERSED IN AN AQUEOUS MEDIUM IN THE PRESENCE OF AN OXIDANT AND IN THE PRESENCE OF AN ACTIVATOR COMPOSITION PREPARED BY DISSOLVING IN WATER A SALT OF A MULTIVALENT METAL CAPABLE OF EXISTING IN TWO VALENCE STATES UNDER SUCH CONDITIONS THAT IT IS PRESENT AT LEAST IN PART IN A LOWER VALENCE STATE TOGETHER WITH A PYROPHOSPHATE OF A MONOVALENT CATION SELECTED FROM THE CLASS CONSISTING OF ALKALI METALS AND AMMONIUM AND WITH A REDUCING SALT OF A MONOVALENT CATION SELECTED FROM THE CLASS CONSISTING OF ALKALI METALS AND AMMONIUM AND OF AN INORGANIC ANION SELECTED FROM THE CLASS CONSISTING OF HYPOPHOSPHITE, THIOSULFATE, SULFITE, BISULFITE AND HYPOSULFITE, HEATING SAID SOLUTION TO 40 TO 100* C. FOR 5 TO 90 MINUTES AND SUBSEQUENTLY COOLING SAID SOLUTION, AND ADDING THE COOL SOLUTION TO SAID AQUEOUS DISPERSION, THE AMOUNT OF SAID SOLUTION ADDED AND THE AMOUNT OF SAID CONSTITUENTS PRESENT IN SAID DISPERSION BEING SUCH THAT, PER 100 PARTS BY WEIGHT OF SAID MONOMERIC MATERIAL, THERE IS ADDED 0.01 TO 1 MILLIMOL PART OF EACH OF SAID MULTIVALENT METAL AND PYROPHOSPHATE AND 0.02 TO 1 PART OF SAID REDUCING SALT, AND SAID OXIDANT IS PRESENT IN AN AMOUNT IN EXCESS OF ONE MOLECULAR EQUIVALENT OF SAID MULTIVALENT METAL. 